1. Field of the Invention
The present invention concerns a wind power installation having a generator which has a stator in which grooves are provided at the inner or outer periphery in mutually spaced relationship to receive a stator winding. Such wind power installations are known and are produced and marketed for example by ENERCON.
2. Description of the Related Art
A known process for the production of stator windings in generators includes the use of what are referred to as former-wound coils. Those former-wound coils are individual windings of the stator winding, which are already adapted in respect of their form to the grooves and groove spacings of the stator and which are firstly individually inserted into the grooves and then connected together.
It will be appreciated however that wind power installations are always exposed to high levels of loading during operation thereof. With an increasing wind speed the power output of the wind power installation increases but at the same time the mechanical loading also rises. That means that the stress on the wind power installation increases substantially simultaneously, from the mechanical and the electrical point of view. At high wind speeds the mechanical stress on the installation is high and at the same time a great deal of electrical power is generated so that the stress on the electrical components is also high.
In that situation, the generator of the wind power installation, which is subjected to mechanical and electrical stresses, is particularly stressed. That combination gives rise to problems if for example, as a consequence of high electric currents generated, the temperature in the region of the generator is also high and, as a consequence of mechanical stress, connections between individual components are subjected to the effect of vibration. If thermal expansion also gives rise to a small amount of play or a loosening effect, the mechanical loadings can here result in a defect or even damage.
If that trouble involves the stator winding or a phase thereof, at least that phase is out of commission in terms of energy production. Furthermore this involves an additional asymmetrical loading in the generator as, as a consequence of the interruption, that phase acts as in the no-load mode of operation. In that respect mechanical damage due to released and freely movable components such as connecting sleeves is not even taken into consideration.
In the case of a stator, wound in six-phase configuration, of a generator with 72 poles, there are 432 former-wound coils which are connected together by 864 connecting locations. Those connecting locations are usually in the form of screw, clamping or solder connections.
Having regard to statistical probabilities (of no matter how small magnitude), the high number of connecting locations and the permanent changes in load mean that, even if the connection between the former-wound coils is carefully made, this involves a serious source of trouble. In that respect only one stator is taken into account in the foregoing considerations. The aspect of mass production clearly reveals the actual probability of such a problem occurring.